http://dx.doi.org/10.1590/S0365-05962010000400023

IM.D.; Specialization in Dermatology (in progress) at the Health Sciences Federal University of Porto Alegre (UFCSPA) - Porto Alegre (RS), BrazilIIPh.D. in Medical Sciences from the Federal University of Rio Grande do Sul (UFRGS); Professor (Ph.D.) of Dermatology at the Health Sciences Federal
University of Porto Alegre (UFCSPA) and Professor of the Postgraduate Program in Pathology at the Health Sciences Federal University of Porto Alegre (UFCSPA)
- Porto Alegre (RS), BrazilIIIPathologist Physician; M.S. from the European Institute of Oncology; Specialization in pathological anatomy from the Porto Alegre Clinical Hospital (HCPA) - Porto Alegre (RS), BrazilIVM.D. - Specialization in Dermatology from the Health Sciences Federal University of Porto Alegre (UFCSPA) - Porto Alegre (RS), BrazilVM.D. - Specialization in Internal Medicine from the General Hospital of Caxias do Sul - Caxias do Sul (RS), Brazil

Lichen nitidus is a rare dermatosis, characterized by round, skin-colored papules whose size varies between 1-2 mm and are generally asymptomatic. It does not have predilection for gender or race, affecting mainly children and young adults. Its clinical course is unpredictable, but most cases tend to spontaneously regress years after the onset of the disease. Lesions are often localized, but rare reports of disseminated disease exist.

Keywords: Lichen nitidus; Lichenoid eruptions; Lichens

HISTORY OF THE DISEASE

Male patient, seven-years-old, with a history of
discrete pruriginous skin lesions for 18 months. Lesions first appeared on his forearms
and rapidly disseminated. The patient denied the use of previous medication, comorbidities
or familial history of skin lesions. Physical examination revealed small, nonscaly,
smooth and shiny skin-colored papules, with 1-2 mm of diameter, affecting nearly
all his skin, sparing only nails, palmoplantar regions, mucous membranes, and part
of his hair scalp (Figures 1, 2).

Described for the first time in 1901 by Pinkus 1,2 as a variant of lichen planus, and once treated as a tuberculosis lesion due to its
granulomatous histopathologic aspect, lichen nitidus is a rare, chronic idiopathic
dermatosis that affects mainly children and young adults. It is characterized by
multiple circumscribed monomorphic papules, skin-colored and shiny, whose diameter
varies between 1-2 mm and are often asymptomatic (some patients report pruritus).
There is no predilection for sex or race and its clinical course is unpredictable.
Most cases tend to spontaneously regress years after the onset of the disease. It
is often localized, rarely disseminated, affects mostly the genital region, upper
extremities, thorax and abdomen. 1-10 Occasionally, palmoplantar, oral
and nail lesions (thickening, linear striations, pittings, and roughness) can be
observed. 5,7-10 There are atypical forms of the disease, described as
keratodermic, follicular, vesicular, hemorrhagic, petechiae or perforating; 5,7-10 Köebner's phenomenon can also be found. 1,2,4,5,7

The histopathology of this dermatosis is fairly
typical, described as a lymphohistiocytic dermal infiltrate, sharply demarcated and
round, surrounded by hyperplastic dermal pappilae (classically known as the "ball
and clay" infiltrate), and parakeratosis with epidermal atrophy right above the infiltrate. 1-5,7-10 Degenerative alterations of the basement layer, identical to
those found in lichen planus lesions, may be seen, but contrary to lichen planus,
direct immunofluorescence on lichen nitidus does not usually reveal immunoglobulin
or complement deposits. 1,7

Although clinically and histologically distinct,
lesions of lichen nitidus and lichen planus may coexist in the same patient (in about
30% of the cases of lichen nitidus), and the possibility that lichen nitidus is a
clinical variant of lichen planus has never been completely dismissed. 2,4,5,7-9

Since lichen nitidus is a localized, asymptomatic
disease that tends to remit, the objective of treatment in most cases is to alleviate
the symptoms. The disseminated form of the disease has a more unpredictable clinical
course, oftentimes longer. Currently, there is no consensus about the best treatment
option. 1-10 In addition to antihistamines, topical and systemic corticosteroids,
retinoids, cyclosporine, tuberculostatic drugs, itraconazole, dihydrochlorobenzene
and ultra-violet A and B phototherapy are treatment alternatives found in the literature. 1,2,4-10